The most incendiary evidence presented in court last January in the effort to overturn California's Proposition 8 -- the ban on same-sex unions adopted by the state's voters in 2008 -- dealt with whether prejudice had motivated the ban's advocates. Video footage and documents from the "Yes on 8" campaign showed its organizers claiming, for example, that gays are 12 times more likely than straight people to molest children and that the "homosexual agenda" includes legalizing pedophilia. If gay marriage were allowed to continue in California, one "Yes on 8" organizer wrote, "every child, when growing up, would fantasize [about] marrying someone of the same sex." And if the measure did not pass, he warned, the states would fall "one by one into the hands of Satan." In a simulcast rally, campaigners compared gay marriage to September 11.

To many Americans, it seems bizarre to think of gay marriage as a threat comparable to terrorism. Those who have gay friends see them pursuing fulfillment in familiar ways: raising healthy children, working, and living beside us. Nonetheless, Proposition 8's campaigners seem to have tapped into a feeling shared by enough California voters to get the measure passed. In her new book, From Disgust to Humanity, University of Chicago philosopher Martha Nussbaum argues that visceral appeals to disgust -- as opposed to rational principles -- lie at the heart of contemporary laws targeting gay people, particularly gay men. Some philosophers and ethicists have defended the use of disgust as a moral barometer, but Nussbaum contends that such an approach is incompatible with the goals of a fair and equitable society.

What may be surprising to some is that laws targeting gays and lesbians are, in historical terms, fairly recent. Although Anglo-American legal tradition has long included laws against sodomy, these prohibitions were part of general bans on non-procreative sexual activity; it was only in the late 19th century that specific laws were enacted targeting "homosexual acts." Nussbaum hazards that the shift is related to Victorian morality, but a more compelling explanation is that laws targeting gays and lesbians came about simultaneously with the emergence of the homosexual as a social identity in the 19th century. A distinct identity and targeted repression came together.

Three pivotal cases lie at the heart of modern gay-rights law: Bowers v. Hardwick (1986), which upheld a Georgia ban on sodomy; Romer v. Evans (1996), which held that anti-gay "animus" provided insufficient justification for denying gays and lesbians equal protection; and Lawrence v. Texas (2003), which decriminalized sodomy nationwide, overturning Bowers. Nussbaum focuses primarily on Bowers, a striking affirmation of the "politics of disgust" that the book sets out to rebut.

As the Supreme Court would note 20 years later, Bowers dwelled on the act of sodomy instead of addressing the broader question of whether the Constitution protects private, consensual sex between adults. When the Court ruled in favor of the Georgia ban on sodomy, Justice Byron White focused exclusively on "homosexual sodomy" (despite the fact that sodomy is also a common heterosexual practice) and declared the claim of a "Constitutional right to homosexual sodomy" to be "facetious." The justices' narrow fixation on gay sex is a subtle indicator of the politics of disgust at play, but explicit appeals to disgust were a staple of the defense's strategy. In oral arguments, Georgia Attorney General Michael Bowers insisted that "homosexual sodomy [leads] to other deviant practices such as sadomasochism, group orgies, or transvestism." Hardly a rational argument, his presentation relied on an ingrained aversion to gay sex and drew unsupported links to other foci of disgust.

Reliance on disgust as a justification for discriminatory law has been pervasive more recently as well. Paul Cameron, the founder and head of the Family Research Institute, was instrumental in passing Amendment 2 in Colorado, a voter initiative that in 1992 barred any city in the state from passing nondiscrimination ordinances that protected gays and lesbians. Cameron has written extensively on the supposed medical consequences of homosexuality: "Imagine exchanging saliva, feces, semen and/or blood with dozens of different men each year. ... Further, many of [these practices] occur in extremely unsanitary places (bathrooms, dirty peep shows), or, because homosexuals travel so frequently, in other parts of the world." Cameron's extreme views led to his expulsion from the American Psychological Association in 1983. The American Sociological Association has also condemned his "misrepresentation of sociological research" and "repudiated any claims that [he] is a sociologist." Yet in 2003, the judges dissenting from the Massachusetts Supreme Court decision legalizing same-sex marriage cited research from Cameron about the "emotional disturbance and sexual victimization" of children raised by same-sex parents as a rational basis for banning same-sex marriage. Less fervent opponents of homosexuality are quick to differentiate themselves from Cameron, but as Nussbaum convincingly shows, appeals to disgust are a central component of anti-gay argument.

In 1997, Leon Kass, a medical ethicist who chaired President George W. Bush's bioethics council, published an essay in The New Republic defending "the wisdom of repugnance" as a basis for law. "In crucial cases," he writes, "repugnance is the emotional expression of deep wisdom, beyond reason's power to fully articulate it." Nussbaum's view is the opposite. Wisdom that cannot be articulated is, for her, no wisdom at all.

In some instances, Nussbaum concedes, disgust signals a reasonable aversion to substances that are actually harmful. Researchers in social science and biology have shown that disgust serves the evolutionary purpose of warning against contamination by disease, in particular when it involves waste products or rotting flesh. But feelings of revulsion are unreliable. They have also been directed at substances that pose little danger, such as certain foods. Most important, disgust is often directed at unpopular minorities -- Jews, intermarried couples, people with disabilities. Nussbaum calls the latter "projective disgust," and its central function is to associate individuals and groups with "primary objects of disgust." In this vein, gays are portrayed as agents of disease and as threats to cleanliness (moral and otherwise) and are directly associated with feces, blood, and semen. For straight men, the book argues, this fear of contamination is further compounded by anxieties about penetration, the "sacred boundary against stickiness, ooze, and death." Disgust toward people naturally assumes a power dimension; a powerful majority is never the subject of these emotions. Though Nussbaum does not say so explicitly, it seems projective disgust is a maladaptive generalization of this biologically endowed emotion.

From Disgust to Humanity concludes that all forms of disgust are problematic as a basis for law. People are repelled by acts of violence or rape, but there are independent, rational justifications for laws against those harms. For this reason, Nussbaum dedicates some time to debunking the attempts to make a rational case for laws punishing homosexuality. We do not, for instance, ban other forms of sex that are non-procreative, nor do we otherwise restrict marriage to those citizens society judges morally upstanding. Nussbaum demonstrates convincingly that the arguments offered by anti-gay crusaders ultimately rely on disgust to animate them.

The danger in relying solely on disgust to guide public policy and law is that feelings of revulsion are socially mediated and, in the absence of reason, justification by disgust is tautological. There is no shortage of historical examples showing the danger of socially ingrained emotions unmoored from reason.

Ten years after Bowers, the Supreme Court recognized this inherent problem when it overturned the Colorado ban on anti--discrimination laws. In Romer, the Court held that bare "animus" toward gays and lesbians -- the moral revulsion toward gay people or gay sex -- is insufficiently "rational" to deny them equal protection under the Constitution.

Given Romer's stunning rebuke to disgust as a basis for law, the defenders of Proposition 8 struggled to provide a rationale for a law that draws a value distinction between gays and heterosexuals. In an oft-quoted exchange between Judge Vaughn Walker and defense attorney Charles Cooper in the federal marriage case, Vaughn asked Cooper how gay marriage would harm straight marriage. "I don't know," Cooper responded. As the trial progressed, it became increasingly clear that the threats envisioned by Proposition 8's backers had little reality to them: Defense lawyers did not bother trying to show that gays are more likely to molest children, and they were unable to present witnesses who could testify that children raised by same-sex parents fare any worse than those raised by heterosexuals. During testimony from one defense expert about the negative effect of same-sex marriage on society, the judge said that if the case were being tried before a jury, the witness would not be permitted to testify as an expert.

Nussbaum attributes the recent legal gains that gays and lesbians have made to a "politics of humanity" that has replaced disgust with empathy -- or "imagination" as Nussbaum puts it -- and understands gay people as equals pursuing happiness in good conscience. In the evolution from disgust to humanity, Bowers v. Hardwick and Lawrence v. Texas lie on opposite sides of a great divide. In overturning Bowers, the justices in Lawrence ruled that the narrow framing the Court had offered was "demeaning," "just as it would demean a married couple were it said that marriage is just about the right to have sexual intercourse." Justice Anthony Kennedy, delivering the opinion of the court, recognized that the "liberty protected by the Constitution allows homosexual persons the right to choose to enter upon relationships in the confines of their homes and their own private lives and still retain their dignity as free persons."

What changed between Bowers and Lawrence? What caused the court to consider gays as human beings pursuing fulfillment and not as perpetrators of deviant acts? If there is any critique to be levied at Nussbaum's otherwise eloquent case against the politics of disgust, it is her failure to recognize the larger social context of the changes that have now taken place. The book's final chapter ties the evolution of legal and social attitudes toward gays to movies such as Milk, which "have given us many powerful images of gay and lesbian lives." The role of the arts in humanizing gay people is undeniable, but the change in attitudes toward gays and lesbians makes sense only on the shoulders of the women's and civil-rights movements, which provided a template, and the AIDS epidemic, which made gay rights a matter of survival. The AIDS crisis and the activism it engendered are often said to have made gays and lesbians "visible," but visibility is not tantamount to liberation. The increased visibility of gays and lesbians after the 19th century made them targets of greater discrimination. The women's and civil-rights movements, however, challenged the public and the courts to look beyond gender and biology and imagine what it is like to be on the other side of these divides. That enlarged vision opened the way for a more humane politics to begin to overcome the politics of disgust.

About the Author

Gabriel Arana is a senior editor at The American Prospect. His articles on gay rights, immigration, and media have appeared in publications including The New Republic, The Nation, Salon, The Advocate, and The Daily Beast.